/**
 * Created with IntelliJ IDEA
 * Description:
 * User: Administrator
 * Data: 2023 - 05 - 24
 * Time: 14:46
 */
// 2、无头双向链表实现
public class LinkedList {
    static class LinkNode {
        public int val;
        public LinkNode prev;
        public LinkNode next;
        public LinkNode(int data) {
            this.val = data;
        }
    }
    public LinkNode head;
    public LinkNode last;
    //得到单链表的长度
    public int size() {
        int count = 0;
        LinkNode cur = head;
        while(cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }
    public void display() {
        LinkNode cur = head;
        while(cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        LinkNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
        //头插法
        public void addFirst(int data) {
          LinkNode cur = new LinkNode(data);
          if(head == null) {
              head = cur;
              last = cur;
              return;//如果有else这里就不用加return
          }
          cur.next = head;
          head.prev = cur;
          head = cur;
        }
        //尾插法
        public void addLast(int data) {
            LinkNode cur = new LinkNode(data);
            if(last == null) {
                head = cur;
                last = cur;
                return;
            }
            last.next = cur;
            cur.prev = last;
            last = cur;//或last=last.next
        }
        //任意位置插入,第一个数据节点为0号下标
        public boolean addIndex(int index,int data) {
            if((index < 0) || (index > size())) {
                throw new IndexOutOfException(index + "下标不合法");
            }
            if(index == 0) {
                addFirst(data);
                return true;
            }
            if(index == size()) {
                addLast(data);
                return true;
            }
            LinkNode node = new LinkNode(data);
            LinkNode cur = head;
            while(index != 0) {
                cur = cur.next;
                index--;
            }
            node.next = cur;//index==size()时这样插入不行，所以index==size()时要单独用尾插法插入
            node.prev = cur.prev;
            cur.prev.next = node;
            cur.prev = node;
            return true;
        }

        //删除第一次出现关键字为key的节点
        public void remove(int key) {
            if(head == null) {
                System.out.println("链表为空");
                return;
            }
            LinkNode cur = head;
            while(cur != null) {
                if(cur.val == key) {
                    if(cur.prev == null) {//删除头节点
                        if(cur.next != null) {
                            head = cur.next;
                            head.prev = null;
                        }else {//只有一个节点，且这个节点是要删除的节点
                            head = cur.next;
                            last = null;
                        }
                    }else {
                        if(cur.next == null) {//删除尾节点
                            cur.prev.next = cur.next;
                            last = cur.prev;
                        }else {
                            cur.prev.next = cur.next;//删除中间节点
                            cur.next.prev = cur.prev;
                        }
                    }
                   return;
                }else {
                    cur = cur.next;
                }
            }
            System.out.println("没有要删除的数据");
        }
        //删除所有值为key的节点
        public void removeAllKey(int key) {
            if(head == null) {
                System.out.println("链表为空");
                return;
            }
            LinkNode cur = head;
            while(cur != null) {
                if(cur.val == key) {
                    if(cur.prev == null) {//删除头节点
                        if(cur.next != null) {
                            head = cur.next;
                            head.prev = null;
                        }else {//只有一个节点，且这个节点是要删除的节点
                            head = cur.next;
                            last = null;
                        }
                    }else {
                        if(cur.next == null) {//删除尾节点
                            cur.prev.next = cur.next;
                            last = cur.prev;
                        }else {
                            cur.prev.next = cur.next;//删除中间节点
                            cur.next.prev = cur.prev;
                        }
                    }
                    cur = cur.next;
                }else{
                    cur = cur.next;
                }
            }
        }

        public void clear() {
            LinkNode cur = head;
            while(cur != null) {
                LinkNode curNext = cur.next;
                cur.next = null;
                cur.prev = null;
                cur = curNext;
            }
            head = null;
            last = null;
        }
}
